Fractionation of hydrogen and oxygen in artificial sea ice with corrections for salinity for determining meteorological water content in bulk ice samples

Artificial seawater is commonly used to recreate arctic conditions in laboratory and mesocosm studies. Baseline oxygen (O) and hydrogen (H) apparent fractionation factor approaching equilibrium (αapp*) and apparent fractionation coefficient approaching equilibrium (εapp*) were determined between artificial seawater and sea ice in conditions representative of mesocosm studies. Laboratory-based values produced under ideal conditions are desired for comparison with natural observations to determine the contribution of meteorological precipitation to mesocosm studies, as opposed to ice formed from seawater. Equilibrium was approached through the use of a closed cold-laboratory freezing method, high mixing rates, and a salinity-correction equation. Apparent fractionation values approaching equilibrium were compared to published equilibrium fractionation values. Fractionation values observed at the Sea ice Environmental Research Facility (SERF) are also reported. We found the following laboratory αapp* and εapp* values, for the freezing of seawater to form sea ice: α18O = 1.0025 ± 0.0002; α2H = 1.0212 ± 0.0005; ε18O (‰) = 2.5 ± 0.2; ε2H (‰) = 21.2 ± 0.5.